PPTC resettable fuse for short circuit protection

[dano12]

Has anyone used these before in the context of a 9vDC-18vDC pedal?

I'm looking through some datasheets and trying to wrap my head around how to employ them....

http://en.wikipedia.org/wiki/Polyswitch

[zyxwyvu]

I used some in my spyder power supply. What I did is put one in series with V+ (in between the rectifier/cap and regulator I believe) for each section. They work fine, and not needing to replace fuses is very handy. The mouser part number of the 250mA ones I used is 576-060R0025U.

[rustypinto]

The above Mouser p/n works, i also use this one:

650-RXEF020-2

These work great with zeners or even TVS diodes to double for over-voltage and reverse voltage events, and then over-current that the PTC takes care of. Eg. Supply (+) > PTC > Zener/ TVS anode (cathode to ground).

I've used this set up to effectively clamp a continuous input supply from 9-18V with an output of ~8.5-11.5V @ 100-150mA load with above mentioned PTC and beefy (5W) TVS. My particular purpose in using this setup is to protect the in-circuit supplies/ biasing for a BBD line. The key here is the PTC response for the "trip current," the load (and variation), and how much current the clamping device begins using when it turns on.

Also note (for what its worth), PTC characteristics can change once they're "tripped" (mainly on-state resistance increases resulting in more DC loss).